Answer this question truthfully
### Question: What causes Juvenile idiopathic arthritis?
### Response: The cause of JRA is not known. It is thought to be an autoimmune illness. In this type of condition, the body's immune system mistakenly attacks and destroys healthy body tissue.
It is divided into several categories:
Systemic JRA involves joint swelling or pain, fevers, and rash. It is the least common category. Polyarticular JRA involves many joints. This form of JRA may turn into rheumatoid arthritis. It may involve large and small joints of the legs and arms, as well as the TMJ and cervical spine. Pauciarticular JRA involves only a few joints, usually the hips, knees, or ankles.